[api-extractor] ExtractorConfig fails when bundled into ESM output

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
72/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
nodejs, typescript
Domain
build-system, tooling

Research direction

Start at the ExtractorConfig._defaultConfig initialization and inspect how schemas/api-extractor-defaults.json is loaded. Reproduce the failure by bundling @microsoft/api-extractor into a single-file ESM output with a listed bundler, then verify that the default schema loads from the bundled output without a runtime filesystem path dependency.

Written by the indexing model from the issue text.

Description

When @microsoft/api-extractor is bundled into a single-file ESM output (e.g. with esbuild, rollup, rolldown, or webpack), the following error is thrown at runtime:

Error: File does not exist: /path/to/bundle-output/schemas/api-extractor-defaults.json

Root cause

ExtractorConfig loads its default config at module initialization time using a __dirname-relative path:

ExtractorConfig._defaultConfig = JsonFile.load(path.join(__dirname, '../schemas/api-extractor-defaults.json'));

__dirname is a CJS-only global — it doesn't exist in ESM. To handle this when bundling CJS code into ESM output, bundlers inject a replacement. For example, rolldown's recommended workaround is to globally define __dirname as import.meta.dirname via transform.define. This replacement resolves to the bundle's output directory rather than the original api-extractor package directory, so the schema file is never found.

Suggested fix

Replace the filesystem read with a static JSON import, which bundlers inline at build time:

import defaultConfig from '../schemas/api-extractor-defaults.json' with { type: 'json' };
ExtractorConfig._defaultConfig = defaultConfig;

This eliminates the runtime filesystem dependency entirely and works correctly whether the package is used directly or bundled.

Dominant language
TypeScript
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Merged PRs (30d)
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